The effects of daytime melatonin ingestion on arousal and vigilance vanish after sub-maximal exercise: a pilot study.

OBJECTIVE: Daytime melatonin ingestion is known to induce sleep at rest, which may affect arousal and vigilance. Physical exercise is known to produce an increase in core temperature and circulating cortisol which can enhance arousal and vigilance. The effect of submaximal exercise on vigilance and arousal following acute melatonin ingestion has not yet been studied. The present study aimed at investigating the effect of submaximal exercise on vigilance and arousal following daytime melatonin ingestion. PATIENTS AND METHODS: Eight physical education students undertook 45 min of submaximal exercise (at 60% of maximal aerobic speed) on a treadmill after melatonin-(6 mg) or placebo ingestion, in a randomized and counterbalanced order. RESULTS: Heart rate (HR), rectal temperature (Tre), felt arousal scale (FAS), and thermal sensations (TS) were recorded at baseline (pre-exercise), immediately after exercise (post-exercise), and after 30 min of recovery (30 min post-exercise). Blood was sampled for lactate and cortisol. At 30 min post-exercise, the Tre, HR, blood pressure, lactate, FAS, and TS were measured. The participants performed vigilance tests pre-exercise, post-exercise and 30 min post-exercise. Daytime melatonin ingestion affected arousal and vigilance in the pre-exercise period (p < 0.05) but had no effect on Tre, HR, blood pressure, lactate, TS, arousal, and vigilance measured 30 min post-exercise (p > 0.05). CONCLUSIONS: The negative effects of melatonin ingestion on vigilance and arousal vanished after a 45 min of submaximal exercise. The hypnotic effect of melatonin observed in the pre-exercise dissipated in the post-exercise period, possibly due to the significant elevation of Tre, HR, and cortisol at the end of submaximal exercise.

Effect of melatonin ingestion on physical performance, metabolic responses, and recovery after an intermittent training session.

OBJECTIVES: Fatigue is a limiting factor for sport performance. For this reason, optimal recovery after training is just as critical as the training program itself, if not more. Indeed, there is a need for strategies that can facilitate recovery after training, and one such strategy is the ingestion of supplements like melatonin (MEL). This study aimed to evaluate if MEL intake could improve recovery of athletes after an intermittent training session (ITS). METHODS: Fifteen elite female athletes (17.4 ± 0.4 years, 76.4 ± 5.6 kg, 1.76 ± 0.04 m; mean ± standard deviation) participated in two testing campaigns. During each period, they performed a battery of physical and cognitive tests before and after an ITS, as well as after ingesting MEL (6 mg tablet) or placebo in a randomized design. The ITS comprised the modified agility T-test, squat jump, counter movement jump, maximum standing ball-throw velocity test, maximum jump ball-throw velocity test, and 20-m sprint. Oral temperature (OT) and vigilance were evaluated before and after the ITS. Rating of perceived exertion (RPE), blood lactate [La], and glucose [Gl] were recorded after each ITS. RESULTS: Short-term performance, recovery of physical performance, and OT were not affected by MEL ingestion after the ITS. Moreover, MEL did not affect cognitive performance or RPE scores after the ITS. However, [La] and [Gl] (p < 0.05 for both) were decreased after MEL ingestion. CONCLUSION: MEL has no effect on the recovery of physical performance but may affect glucose utilization and lactate metabolism during the team-handball training session.

Effects of time-of-day on oxidative stress, cardiovascular parameters, biochemical markers, and hormonal response following level-1 Yo-Yo intermittent recovery test.

The aim of this study was to investigate the effect of time-of-day on oxidative stress, cardiovascular parameters, muscle damage parameters, and hormonal responses following the level-1 Yo-Yo intermittent recovery test (YYIRT). A total of 11 healthy subjects performed an intermittent test (YYIRT) at two times-of-day (i.e., 07:00 h and 17:00 h), with a recovery period of ≥36 h in-between, in a randomized order. Blood samples were taken at the rest (baseline) and immediately (post-YYIRT) after the YYIRT for measuring oxidative stress, biochemical markers, and hormonal response. Data were statistically analyzed using one-way and two-way repeated measures ANOVA and Bonferroni test at p < 0.05. Observed power (α = 0.05) and partial eta-squared were used. Our results showed that oxygen uptake (VO2max), maximal aerobic speed, and the total distance covered tended to be higher in the evening (17:00 h). There was also a main effect of time-of-day for cortisol and testosterone concentration, which were higher after the YYIRT in the morning (p < 0.05). The heart rate peak and the rating of perceived exertion scales were lower in the morning (p < 0.05). However, the plasma glucose (p < 0.01), malondialdehyde, creatine kinase (p < 0.01), lactate dehydrogenase (p < 0.05), high-density lipoprotein (p < 0.01), total cholesterol (p < 0.01), and triglycerides (p < 0.05) were higher after the YYIRT in the evening. Low-density lipoprotein, systolic blood pressure, diastolic blood pressure, and lactate levels (p > 0.05) were similar for the morning and evening test. In conclusion, our findings suggest that aerobic performance presents diurnal variation with great result observed in the evening accompanied by an improvement of hormonal, metabolic, and oxidative responses. These data may help to guide athletes and coaches and contribute to public health recommendations on exercise and muscle damage particularly in the competitive periods.

Morning melatonin ingestion and diurnal variation of short-term maximal performances in soccer players.

Aim Very few studies have investigated the temporal specificity of melatonin (MEL) ingestion upon short-term maximal athletic performances. The aim of the present study was to explore the effect of morning MEL ingestion on cognitive and physical performances measured in the afternoon. Methods Twelve soccer players from a Tunisian squad (17.9 ± 1.3 years, 1.74 ± 0.06 m and 62.0 ± 8.8 kg) participated in the present study. They performed two testing sessions at 08:00 h, 12:00 h and 16:00 h after either MEL (5mg) or placebo (PLA) ingestion, in a randomized order. During each period, the participants performed the following cognitive and physical tests: reaction time and vigilance tests, medicine-ball throw (MBT), five jumps, handgrip strength (HG), and agility tests. Results cognitive and physical performances were significantly higher at 16:00 h compared to 08:00 h during the two conditions (p < 0.05). Moreover, performances of MBT and HG were lower in the morning with MEL in comparison to PLA (p < 0.05). However, MEL ingestion did not affect physical and cognitive performances measured at 12:00 h and 16:00 h. Conclusion morning MEL ingestion has no unfavourable effect on afternoon physical and cognitive performances in soccer players.

Influence of warm-up duration and recovery interval prior to exercise on anaerobic performance.

The purpose of the study was to determine the impact of different active warm-up (AWU) durations and the rest interval separating it from exercise on anaerobic performance. Eleven male physical education students (22.6 ± 2.52 years; 179.2 ± 4.3 cm; 82.5 ± 9.7 kg; mean ± SD) participated in a cross-over randomized study, and they all underwent the Wingate test after three AWU durations: 5 min (AWU5), 15 min (AWU15) and 20 min (AWU20), with recovery (WREC) or without a recovery interval (NREC) separating the AWU and anaerobic exercise performance. All the AWUs consisted of pedalling at a constant pace of 60 rpm at 50% of the maximal aerobic power. The rest interval between the end of warm-up and the beginning of exercise was set at 5 min. During the Wingate test, peak power (PP), mean power (MP) and the fatigue index (FI) were recorded and analysed. Oral temperature was recorded at rest and at the end of the warm-up. Likewise, rest, post-warm-up and post-Wingate heart rate (HR) and rating of perceived exertion (RPE) were recorded during each session. The ANOVA showed a significant effect of recovery interval, warm-up duration and measurement point on RPE scores (P<0.001). Although the effect of AWU duration on MP and PP was significant (P<0.05), the effect of the recovery interval on both parameters was not significant (P>0.05). Moreover, the analyses showed a significant interaction between recovery interval and AWU duration (P<0.001 and P<0.05 for MP and PP respectively). The AWU15 duration improves the MP and PP when associated with a recovery interval prior to exercise of 5 min. However, the AWU5 duration allows better improvement of power output when the exercise is applied immediately after the warm-up. Consequently, physically active males, as well as educators and researchers interested in anaerobic exercise, must take into account the duration of warm-up and the following recovery interval when practising or assessing activities requiring powerful lower limb muscle contractions.

Maximal power training induced different improvement in throwing velocity and muscle strength according to playing positions in elite male handball players.

This study was designed to assess the effect of strength and power training on throwing velocity and muscle strength in handball players according to their playing positions. Twenty-two male handball players were assigned to either an experimental group (n=11) or a control group (n=11) (age: 22.1 ± 3.0 years). They were asked to complete (i) the ball throwing velocity test and (ii) the one-repetition maximum (1-RM) tests for the half-back squat, the pull-over, the bench press, the developed neck, and the print exercises before and after 12 weeks of maximal power training. The training was designed to improve strength and power with an intensity of 85-95% of the 1RM. In addition to their usual routine handball training sessions, participants performed two sessions per week. During each session, they performed 3-5 sets of 3-8 repetitions with 3 min of rest in between. Then, they performed specific shots (i.e., 12 to 40). Ball-throwing velocity (p<0.001) was higher after the training period in rear line players (RL). The training programme resulted in an improvement of 1RM bench press (p<0.001), 1RM developed neck (p<0.001) and 1RM print (p<0.001) in both front line (FL) and RL. The control group showed a significant improvement only in ball-throwing velocity (p<0.01) and 1RM bench press (p<0.01) in RL. A significantly greater improvement was found in ball-throwing velocity (p<0.001), 1RM bench press (p<0.001), and 1RM half-back squat exercises in players of the central axis (CA) compared to the lateral axis (LA) (p<0.01). The power training programme induced significantly greater increases in ball-throwing velocity and muscle strength in FL than RL and in CA than LA axis players.

Rapid weight loss in the context of Ramadan observance: recommendations for judokas.

Judo is a weight-classified combat sport, and many athletes seek to compete at the lightest possible weight category to gain an advantage from competing against shorter/smaller, and supposedly weaker opponents. To achieve a desired weight, most judokas opt for rapid weight loss techniques. Short-duration maximal efforts are not greatly affected by "making weight", but prolonged and/or repeated exercise is significantly impaired. Negative effects on mood, ratings of perceived exertion, and cognitive function are also reported. Moreover, rapid weight loss reduces maximal cardiac output and glycogen stores, and impairs thermo-regulation. Limited empirical data suggest that Ramadan reduces judokas' performance, and this is likely to be exacerbated by attempts at rapid weight loss. Weight reduction during Ramadan tends to be counterproductive, and judokas who aim for a lower weight category are advised to attempt any desired reduction of body mass during the weeks leading up to Ramadan, rather than during the holy month.

Relationship between biomarkers of muscle damage and redox status in response to a weightlifting training session: effect of time-of-day.

The aims of the present study were to: (1) investigate the effect of a weightlifting training session and time-of-day (TOD) upon biological parameters (i.e., oral temperature, hematological, C-reactive protein (CRP), and oxidative stress) and (2) assess their possible link with muscle damage responses. Nine weightlifters (21 ± 0.5 years) performed, in a randomized order, three Olympic-Weightlifting sessions (i.e., at 08:00, 14:00, and 18:00). Blood samples were collected at rest, 3 min and 48 h after each training session. Between pre- and post-training session, ANOVA showed significant increases in oxidative stress markers at the three TODs (p < 0.01) and significant increases for creatine kinase (CK) and lactate dehydrogenase (LDH) only at 08:00 and 18:00 (p < 0.05). At rest, the results showed a significant diurnal variation for the majority of the selected parameters except for malondialdehyde (MDA), total bilirubin, and CRP with higher values observed at 18:00 (p < 0.05). After the training session, given the higher rate of increase during the morning session, these diurnal variations persisted for temperature and WBC (p < 0.01) and were suppressed for CK, LDH, uric acid (UA), catalase, and glutathione peroxidase. The main significant correlations (p < 0.001) were observed between: (1) CK and MDA (r = 0.6) and CK and UA (r = 0.66 and r = 0.82) during the morning and evening training sessions; (2) CK and CRP only during the morning session (r = 0.5); and (3) CRP and WBC during the three training sessions (r = 0.8). In conclusion, the present findings: (1) confirm that the muscle damage responses could be induced by a high level of oxidative stress and (2) suggest to avoid scheduling training sessions in the morning given the higher muscle damage, inflammatory, and oxidative responses at this TOD.

Aerobic and anaerobic determinants of repeated sprint ability in team sports athletes.

The aim of this study was to examine in team sports athletes the relationship between repeated sprint ability (RSA) indices and both aerobic and anaerobic fitness components. Sixteen team-sport players were included (age, 23.4 ± 2.3 years; weight, 71.2 ± 8.3 kg; height, 178 ± 7 cm; body mass index, 22.4 ± 2 kg · m(-2); estimated VO2max, 54.16 ± 3.5 mL · kg(-1) · min(-1)). Subjects were licensed in various team sports: soccer (n = 8), basketball (n = 5), and handball (n = 3). They performed 4 tests: the 20 m multi-stage shuttle run test (MSRT), the 30-s Wingate test (WingT), the Maximal Anaerobic Shuttle Running Test (MASRT), and the RSA test (10 repetitions of 30 m shuttle sprints (15 + 15 m with 180° change of direction) with 30 s passive recovery in between). Pearson's product moment of correlation among the different physical tests was performed. No significant correlations were found between any RSA test indices and WingT. However, negative correlations were found between MASRT and RSA total sprint time (TT) and fatigue index (FI) (r = -0.53, p < 0.05 and r = -0.65, p < 0.01, respectively). No significant relationship between VO2max and RSA peak sprint time (PT) and total sprint time (TT) was found. Nevertheless, VO2max was significantly correlated with the RSA FI (r = -0.57, p < 0.05). In conclusion, aerobic fitness is an important factor influencing the ability to resist fatigue during RSA exercise. Our results highlighted the usefulness of MASRT, in contrast to WingT, as a specific anaerobic testing procedure to identify the anaerobic energy system contribution during RSA.

Effect of the number of sprint repetitions on the variation of blood lactate concentration in repeated sprint sessions.

The aim of the present study was to examine the effect of number of sprint repetitions on the variation of blood lactate concentration (blood [La]) during different repeated-sprint sessions in order to find the appropriate number of sprint repetitions that properly simulates the physiological demands of team sport competitions. Twenty male team-sport players (age, 22.2 ± 2.9 years) performed several repeated-sprint sessions (RSS) consisting of 1, 2, 3, 4, 5, 9, or 10 repetitions of 30 m shuttle sprints (2 × 15 m) with 30 s recovery in between. The blood [La] was obtained after 3 min of recovery at the end of each RSS. The present study showed that for RSS of 3 sprints (RSS3) there was a high increase (p<0.001) in blood [La], which reached approximately fivefold resting values (9.4±1.7 mmol · l(-1)) and then remained unchanged for the RSS of 4 and 5 sprints (9.6±1.4 and 10.5±1.9 mmol · l(-1), p=0.96 and 0.26, respectively). After RSS9 and RSS10 blood [La] further significantly increased to 12.6 and 12.7 mmol · l(-1), p<0.001, respectively. No significant difference was found between RSS3, RSS4 and RSS5 for the percentage of sprint speed decrement (Sdec) (1.5±1.2; 2.0±1.1 and 2.6±1.4%, respectively). There was also no significant difference between RSS9 and RSS10 for Sdec (3.9±1.3% and 4.5±1.4%, respectively). In conclusion, the repeated-sprint protocol composed of 5 shuttle sprint repetitions is more representative of the blood lactate demands of the team sports game intensity.

Reliability and validity of a new maximal anaerobic shuttle running test.

The purpose of this study was twofold: first to assess the relative and absolute reliability of a new Maximal Anaerobic Shuttle Running Test (MASRT), and second to evaluate the criterion validity of the MASRT. 16 team sport players participated in this study. The velocity (VMASRT) and the number of shuttles achieved at volitional exhaustion were measured. To assess the reliability of the MASRT, each player performed the MASRT twice, on separate days. The criterion validity of the MASRT was determined by examining the relationship between MASRT indices and the Wingate test (WingT) performances. Results showed no difference between test-retest MASRT scores for VMASRT and the number of shuttles (P>0.05). The intraclass correlation coefficients (ICC) values for VMASRT and Shuttle number were 0.84 and 0.80, respectively. The coefficients of variation (CV) and the mean difference (bias)±the 95% limits of agreement for the same variables were 3.6 and 12.9%, and 0.02±0.37m·s-1 and 0.3±6.7, respectively. The strongest correlation was found between mean power output relative to body mass (MPO) measured during the WingT and VMASRT (r=0.77, P<0.001). The MASRT constitutes a reliable and valid field tool for assessing short term repeated running capacity of team sport players.

Reducing resistance training volume during Ramadan improves muscle strength and power in football players.

We aimed to examine the effect of maintaining or reducing resistance training volume during Ramadan-intermittent-fasting (RIF) on short-term maximal performances. 20 footballers (age: 18.4 ± 0.8 years; body-mass: 72.4 ± 4.1 kg; height: 183.4 ± 4.6 cm) were matched and randomly assigned to a normal-training-group (G1) or a tapering-group (G2). They were tested for muscular strength (maximal-voluntary-contraction) and power (squat-jump and counter-movement-jump) 1 month before RIF (T0), 1 week before RIF (T1), after 2 weeks of fasting (T2) and at the end of RIF (T3). From T1 to T2, subjects performed a whole-body resistance training program (8-repetitions × 4-sets with 4-min recovery in-between). During RIF, G1 maintained the same training program, while G2 performed a period of reduced training volume (3 sets/exercise; - 22%). Muscle strength and power increased significantly from T0 to T1, from T0 to T2 and from T0 to T3 in G1 and G2 and from T1 to T2 and from T1 to T3 only in G2 (p<0.05). Performance was higher in G2 than G1 during T2 (p<0.01). Moreover, the ∆-change of performance between T0 and T2 and T3 was significantly higher in G2 than G1 (p<0.05). For young soccer players, a tapering period characterized by a reduced training volume during RIF may lead to significant improvement in muscle strength and power.

Time of day effects on repeated sprint ability.

The present study aimed at investigating the effects of time-of-day on muscle power and associated electromyographic (EMG) activity level of 4 thigh muscles during a repeated pedalling sprint exercise. After a familiarization session, 12 male subjects were asked to perform the repeated sprint ability test during 2 experimental sessions (randomized order), which were set up either at 06:00 or 18:00 h. For each sprint, peak power output, percentage of peak power decrement and total work were calculated. EMG activity of vastus lateralis, rectus femoris, vastus medialis and biceps femoris muscles was recorded throughout the test and analyzed for each sprint. Total work and percentage of peak power decrement were higher in the evening than in the morning (p<0.01 and p<0.05, respectively). Likewise, peak power was significantly higher at 18:00 than 06:00 h during the first 3 sprints (p<0.01 for sprint 1 and p<0.05 for sprint 2 and 3). There was no time-of-day effect for EMG activity level. The neuromuscular efficiency decreased significantly over the repeated sprint ability test at the 2 times of testing (p<0.01). Despite diurnal fluctuation in muscular power and neuromuscular fatigue during the repeated sprint ability test, EMG activity of major thigh muscles was not time-of-day dependent.

High intensity exercise affects diurnal variation of some biological markers in trained subjects.

The study investigated if markers of muscle injury and antioxidant status were affected by a Wingate test performed at 2 different times of day. 15 young male footballers performed 2 tests (randomized) at 07:00-h and 17:00-h. Fasting blood samples were collected before and 3 min after each test for assessment of markers of muscle injury and antioxidant status. Resting oral temperature was recorded during each session. Peak power (10.76 ± 1.05 vs. 11.15 ± 0.83 W.kg( - 1)) and fatigue index (0.41 ± 0.04 vs. 0.49 ± 0.13%) during the Wingate test, and core temperature, were significantly higher (all p<0.05) in the evening. Markers of muscle injury were significantly higher in the evening before and after exercise (e. g., 148.7 ± 67.05 vs. 195 ± 74.6 and 191.6 ± 79.52 vs. 263.6 ± 96.06 IU.L (- 1), respectively, for creatine kinase; both p<0.001). Antioxidant parameters increased after the Wingate test but only resting values were significantly higher in the morning (e. g., 1.33 ± 0.19 vs. 1.19 ± 0.14 µmol.L (- 1) for total antioxidant status; p<0.05). The results indicate that muscle injury and antioxidant activity after the Wingate test were higher in the evening, suggesting a possible link between the biochemical measures and the diurnal fluctuation of anaerobic performance. However, repetition of this study after prescribed rather than self-selected exercise intensity is recommended.

The effect of time-of-day and Ramadan fasting on anaerobic performances.

This study was designed to assess the effects of Ramadan-intermittent-fasting (RIF) and time-of-day on muscle power and fatigue during the Wingate test. In a randomized design, 10 football players completed a Wingate test at 07:00 and 17:00 h on 3 different occasions: one week before Ramadan (BR), the second week of Ramadan (SWR) and the fourth week of Ramadan (ER). There was an interval of 36-h between any 2 successive tests. During the Wingate test, peak power (PP), mean power (MP) and the fatigue index (FI) were recorded. While PP, MP and FI were greater in the evening than in the morning during BR (p<0.001), these diurnal variations in muscle power disappeared during the month of Ramadan (i. e., SWR and ER) due to a significant decrease in PP and MP in the evening (p<0.001). However, the diurnal variation in FI when measured at 17:00 h increased during this month (p<0.001). In addition, ratings of perceived exertion and fatigue were higher in the evening during Ramadan in comparison with BR. These results suggest that Ramadan might modify the circadian rhythm of muscle power and fatigue during the Wingate test by decreasing power output and increasing muscle fatigue at the time of the acrophase.

Listening to music affects diurnal variation in muscle power output.

The purpose of this investigation was to assess the effects of listening to music while warming-up on the diurnal variations of power output during the Wingate test. 12 physical education students underwent four Wingate tests at 07:00 and 17:00 h, after 10 min of warm-up with and without listening to music. The warm-up consisted of 10 min of pedalling at a constant pace of 60 rpm against a light load of 1 kg. During the Wingate test, peak and mean power were measured. The main finding was that peak and mean power improved from morning to afternoon after no music warm-up (p<0.001 and p<0.01, respectively). These diurnal variations disappeared for mean power and persisted with an attenuated morning-evening difference (p<0.05) for peak power after music warm-up. Moreover, peak and mean power were significantly higher after music than no music warm-up during the two times of testing. Thus, as it is a legal method and an additional aid, music should be used during warm-up before performing activities requiring powerful lower limbs' muscles contractions, especially in the morning competitive events.

Circadian rhythms in two types of anaerobic cycle leg exercise: force-velocity and 30-s Wingate tests.

Previous studies investigating the impact of circadian rhythms on performance during anaerobic cycle leg exercise have yielded conflicting results. The purpose of the present investigation was firstly, to determine the effect of the time of day on anaerobic performance during a force-velocity test on a cycle ergometer (F-V) and the Wingate test and secondly, to relate any changes in anaerobic performance to the circadian rhythm in oral temperature. Nineteen subjects volunteered to take part in the study. In a balanced and randomized study design, subjects were measured for maximal power (P (max)) (force-velocity test), peak power (P (peak)) and mean power (P (mean)) (Wingate test) on six separate occasions. These were at 02 : 00, 06 : 00, 10 : 00, 14 : 00, 18 : 00 and 22 : 00 hours on separate days. There was an interval of 28 h between two successive tests. Oral temperature and body mass were measured before each test. Body mass did not vary during the day but a significant time of day effect was observed for the oral temperature with an acrophase at 18 : 22 +/- 00 : 34 hours. A significant circadian rhythm was found for P (max) with an acrophase at 17 : 10 +/- 00 : 52 hours and an amplitude of 7 %. A time-of-day effect was significant for F (0) and V (0). Also a significant circadian rhythm was observed for P (peak) with an acrophase at 17 : 24 +/- 00 : 36 hours and an amplitude of 7.6 % and for P (mean) with an acrophase at 18 : 00 +/- 01 : 01 hours and an amplitude of 11.3 %. The results indicated that oral temperature, P (peak), P (mean) and P (max) varied concomitantly during the day. These results suggest that there was a circadian rhythm in anaerobic performance during cycle tests. The recording of oral temperature allows one to estimate the time of occurrence of maximal and minimal values in the circadian rhythm of anaerobic performance.

Treatment of saline wastewaters from marine-products processing factories by activated sludge reactor.

An activated sludge reactor, operated at room temperature (20-30 degrees C) was used to treat saline wastewaters generated by marine-products industries. The system was operated continuously and the influence of the organic loading rates (OLRs), varying from 250 to 1000 mg COD l(-1) day(-1), on chemical oxygen demand (COD) removal was investigated. The system, inoculated with NaCl-acclimated culture, removed up to 98% and 88% of the influent COD concentrations at OLRs of 250 and 1000 mg COD L(-1) day(-1), respectively. Since the organic pollution is essentially composed of proteins, microorganisms, which produced proteolytic enzymes, were isolated from the activated sludge culture. One bacterium with the highest protease activity, identified as Bacillus cereus, was chosen for protease production in fishery wastewaters of different concentrations containing combined heads and viscera powder. Protease synthesis was strongly enhanced when cells were cultivated in two times diluted fishery wastewaters. The enhancement of protease synthesis could have been due to the presence in effluent of organic matters or salts, which stimulated the growth of the strain and protease production.